ASP.NET

public void get_data()
{
    try
    {
        pro_id = Request.QueryString["pr_id"];
        quanti = Convert.ToInt32(Request.QueryString["quant"]);

        if (pro_id != null)
        {
            SqlConnection con = new SqlConnection("Server=.; Database=eclsc; Trusted_Connection=yes");
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandText = "select ICEMACHINES.product_id,ICEMACHINES.sh_desc,ICEMACHINES.price from ICEMACHINES where ICEMACHINES.product_id LIKE @product_id union select GLASSWARE.product_id,GLASSWARE.sh_desc,GLASSWARE.price from GLASSWARE where GLASSWARE.product_id LIKE @product_id ";
            cmd.Parameters.Add("@product_id", SqlDbType.NVarChar, 50).Value = pro_id;
            cmd.Connection.Open();
            SqlDataReader rdr = cmd.ExecuteReader();
            ArrayList arRole1 = new ArrayList();

            while (rdr.Read())
            {
                desc = (rdr["sh_desc"]).ToString();
                id = (rdr["product_id"]).ToString();
                unitprice = Convert.ToSingle((rdr["price"]));
                cost = unitprice * quanti;

            }
            cmd.Connection.Close();

            DataRow myrow = dt.NewRow();
            myrow["REF"] = id;
            myrow["Description"] = desc;
            myrow["QTY"] = quanti;
            myrow["Price"] = unitprice;
            myrow["Cost"] = cost;

             int dtcount = dt.Rows.Count;
             if (dtcount > 0)
            {
            DataRow[] arrMatchingValues = dt.Select("REF=" + id);
            if (arrMatchingValues.Length > 0)
            {
                DataRow drUpdateMe = arrMatchingValues[0];
                int drUpdateQuant = Convert.ToInt32(drUpdateMe["QTY"]);
                int quan = quanti + drUpdateQuant;
                drUpdateMe["QTY"] = quan;
                dt.AcceptChanges();
            }
            }
            else
            {
                dt.Rows.Add(myrow);
                dt.AcceptChanges();
            }

            Session["data"] = dt;
            GridView1.DataSource = dt;
            GridView1.DataBind();


        }
        else
        {
            int a = 1;
        }
        total_items = total_items + quanti;
        total_Price = total_Price + cost;
        Session["items"] = total_items;
        Session["value"] = total_Price;
    }
    catch(Exception ee)
    {
        Lblmsg.Text = ee.Message;
    }
    }